This project is concerned with understanding extinction, the loss of learned performance that occurs when a Pavlovian signal or an instrumental action is repeatedly presented without its reinforcer. Extinction is a naturally-occurring process of behavior change, as well as a tool used in clinical treatments designed to eliminate unwanted thoughts, emotions, and behaviors in humans. Although it is tempting to assume that extinction erases the original learning, extinguished performance readily recovers, and several recovery effects (e.g., renewal, reinstatement, rapid reacquisition, spontaneous recovery, and resurgence) indicate that the original learning may be largely intact. In addition, because these effects can be interpreted as effects of changing the background or ?context,? they suggest that extinction results from new inhibitory learning that is especially sensitive to the context in which it is learned. The goal of this project is to seek an integrated understanding of extinction as it is revealed in these and other response-recovery processes. It will focus especially on the extinction of instrumental (operant) learning, because principles of operant learning are crucial for understanding a range of behavior problems?such as drug abuse, smoking, and overeating?in which voluntary contact with reinforcers plays an essential role. The experiments will involve rats as subjects. One set will test evidence that the rat learns to actively inhibit its behavior during extinction, and will evaluate an account of how that inhibition is learned. Another set will distinguish between goal-directed actions and automatic habits, and will ask how sensitive they are to extinction, relapse, and other types of behavior change. A third set will analyze learning and extinction of sequences or ?chains? of behavior in which the individual must purchase (or procure) access to the reinforcer before he or she can consume (or ?take?) it. A fourth set of experiments will test new hypotheses about relapse and the prevention of relapse when rats learn to inhibit a response they perform in order to receive intravenous cocaine delivery. The results will increase our understanding of extinction, a fundamental behavioral and clinical phenomenon, and develop new ways to help promote extinction learning so as to minimize lapse and relapse.